Staphylococcus aureus is a major cause of food poisoning in the United States. Staphylococcal food poisoning is an intoxication associated with vomiting and diarrhea. Our lab is concerned with structure-function analysis of staphylococcal enterotoxins, allowing the identification of functional regions necessary to cause symptoms in the gastrointestinal tract. Another important aspect of this work is that it allows us to differentiate between enterotoxic and superantigenic molecular regions. The region implicated most strongly in enterotoxic activity is the area around the disulfide loop. We constructed several mutations in this region and have shown that the resulting proteins are nontoxic when administered orally to pigtailed macaques. We will extend this work during the next year to determine whether protective immunity can be induced in the gastrointestinal tract by using several of these toxins as oral vaccines.